1. Field of the Invention
The present invention relates to a television signal processor for processing different types of television signals transmitted by a different of television systems, e.g., a television signal of an NTSC system or a high definition television signal, and more particularly to a television signal processor, which can display the signal-processed television signal on a large number of types of displays having different synchronizing frequencies and aspect ratios such as a CRT (Cathode Ray Tube) or a liquid crystal projector.
2. Description of the Related Art
Recently in addition to the normal NTSC television system, television signals from a plurality of systems, such as an EDTV system or a MUSE system can be received. Television receivers, are know which can receive a plurality of types of television signals. "National Technical Report Vol. 37 No. 5, Oct. 1991", for example, describes "36-inch type High Definition Receiver TH-36HDl." This television receiver can receive a high definition MUSE broadcast in addition to a BS/UHF/VHF/CATV broadcast of the current NTSC system.
FIG. 1 shows the structure or this type of television receiver. Reference numeral 11 denotes an antenna. Television signals of UHF/VHF/CATV broadcasts are received by the antenna 11. One of the television signal received by the antenna 11 is selected by a tuner 13, which is controlled by a system controller 12, and converted to a base band signal. Thereafter, the base band signal is supplied to one input terminal of a switch circuit 14. The tuner 13 receives the television signals of the normal NTSC system and an EDTV system, and processes each signal.
Reference numeral 15 denotes another antenna. Television signals from BS broadcasts are received by the antenna 15. One of the television signals received by the antenna 15 is selected by a tuner 16, which is controlled by the system controller 12, and converted to a base band signal. Thereafter, the base band signal is supplied to the other input terminal of the switch circuit 14. The tuner 16 receives television signals of the is a high definition MUSE type in addition to the television signals of the normal NTSC system and the EDTV system, and processes each signal.
The switch circuit 14 receives the respective base band signals output from the tuners 13 and 16 and separately outputs a selected one of the received signals to an NTSC decoder 17 and an MUSE decoder 18, 93 The NTSC decoder 17 converts the base band signals received thereby to the respective color signals R (Red), G (Green) and B (Blue), and outputs these signals to a scanning line converter 19.
The scanning line converter 19 converts 525 horizontal scanning lines, corresponding to the number of interlaced lines in the television signals of NTSC system are interlaced, to 525 non-interlaced signals (double-speed conversion). It then outputs these signals to a time compressor 20. The time compressor 20 compresses the received signals to adjust the aspect ratios for display of the respective color signals R, G, B on a CRT when these color signals are displayed on a wide screen. For instance, when the aspect ratio is 16:9, the respective color signals R, G, B are compressed to 3/4 in a horizontal direction. The time-compressed color signals R, G, B are supplied to one input terminal of a switch circuit 21.
The MUSE decoder 18 processes the base band signal of MUSE system which is band-compressed to 8.1 kHz, converts the respective color signals R, G, B generated by the processing, and outputs these signals to the other input terminal of the switch circuit 21. The NTSC decoder 17 and the MUSE decoder 18 fetch a horizontal synchronizing signal H and a vertical synchronizing signal V from the inputted base band signals. The horizontal synchronizing signal H and the vertical synchronizing signal v, which are fetched by the NTSC decoder 17, are supplied to one input terminal of a switch circuit 22. The horizontal synchronizing signal H and the vertical synchronizing signal V, which are fetched by the MUSE decoder 18, are supplied to the other input terminal of the switch circuit 22.
The switch circuit 21 is switched to selectively supply color signals R, G, B, which are obtained by processing the base bands of NTSC system and color signals R, G, B, which are obtained by processing the base bands of MUSE system, to a CRT 23 based on the control of the system controller 12. The switch circuit 22 is switched synchronously with switch circuit 21 based on the control of the system controller 12. In other words, the switch circuit 22 is switched to supply the horizontal synchronizing signal H and the vertical synchronizing signal V, which correspond to the color signals R, G, B supplied to the CRT 23, to a deflection circuit 24.
The deflection circuit 24 is controlled by the system controller 12. When the CRT 23 performs the image-display based on the television signal of NTSC system, the deflection circuit 24 controls the CRT 23 based on the frequency of the horizontal synchronizing signal H of 31.5 kHz and that of the vertical synchronizing signal V of 59.94 Hz. Moreover, the frequency of the horizontal synchronizing signal H in the NTSC system is 15.75 kHz. However, since the television signal is converted at double speed by the scanning line converter 19, the frequency of the horizontal synchronizing signal H is doubled (31.5 kHz) to adjust to the double-speed conversion. Alternatively, when the CRT 23 performs the image-display based on the television signal of MUSE system, the deflection circuit 24 controls the CRT 23 based on the frequency of the horizontal synchronizing signal H of 33.75 kHz and that of the vertical synchronizing signal V of 60 Hz.
The system controller 12 is operated to control a series of tuning operation. For example, system controller 12 may operate based on commands outputted from a control section 26 of a remote-control which are received by receiver 25.
In the above-mentioned television receiver, there exists an integral structure formed from the tuners 13 and 16, to which the television signals are first received by the antennas 11 and 15 and the CRT 23, which actually displays the image. Further, the deflection circuit 24 selectively generates the horizontal and vertical synchronizing signals H and V to control the CRT 23. Therefore, the signal processing section for processing the received television signal corresponds with the display section for image-displaying the signal processed by the signal-processing section. In other words, the signal processing section is designed to correspond to only a particular the display section having a fixed synchronizing frequency and a fixed aspect ratio.
In sum, in conventional television receiver which are designed receive each television signals transmitted by one of a plurality of types of television systems, the signal processing section is designed to correspond to a particular display section having a fixed synchronizing frequency and a fixed aspect ratio. Consequently, the received television signal cannot be adapted to a large number of types of displays having a different synchronizing frequencies and different aspect ratios.
In general, the frequency of the horizontal synchronizing signal necessary for operating a display such as (i.e. CRT) is not limited to the above-mentioned two frequencies particularly when personal computers and work stations are considered. Specifically, many such frequencies may be necessary to accommodate the large number of displays available for personal computers, workstations and the like. For example, there is a horizontal synchronizing signal to be used for a graphic display whose frequency is over 100 kHz. Accordingly, it has become necessary to process the received television signals not only for display on predetermined CRTs but also for displays such as that for a personal computer. In other words, multi-media systems require processing of input signals for a varying number of possible display devices.
Particularly, in recent years, a liquid crystal projector using liquid crystal has been produced on a commercial basis. Soon, in addition to the liquid crystal projector whose current aspect ratio is 4:3 or 16:9, it is expected that the liquid crystal projector, which has an aspect ratio, equivalent to that of a movie screen, will be put into practical use in accordance with the large screen and high definition. Consequently in accordance with the development of the multi-media, it is expected that the signals having a different synchronizing frequencies and a different aspect ratios will become commonplace as shown in the television signals of MUSE and MUSE types in the near future.
In consideration of the above situation, the need for the television receiver such as that disclosed by this invention will dramatically increase.
Generally, in this invention the signal processing section and the display section are separated. The signal processing section can process each television signal transmitted by the plurality of types of the television systems. Furthermore, the processed television signal can be displayed by a large number of types of displays having different synchronizing frequencies and different aspect ratios.